A Step Farther Out (34 page)

And the same is true for other commercial concepts. No one of them is certain to pay for the costs of the system—and nobody wants to get into a number of disparate lines of business, each needed so that the total sum of their incomes will pay for the huge investment. Business doesn't work that way. But here we have a way to pay for the station, so that the fallout discoveries are pure profit.

And at the same time we advance technology, and we reduce payments for foreign oil. If some private firm doesn't leap at this, you'd think the government would. If it appeals to you, write your Congressperson—I'm sure no one in Congress has heard of this scheme.

If all that wasn't enough, there was also Wayne Jones of Lockheed, whose paper was on laser energy relay units.

If you have your power source in LEO it goes into shadow, and you lose power. Not too good. If you put it up in GEO, your laser beam must be exceedingly tightly focused or you're losing energy. Sun and Hertzberg know this, but they've eaten the extra cost to keep the system simple.

The Lockheed group, however, has studied another way. You put your energy source in GEO all right; but then you have several relay stations, which are nothing more than fancy steerable mirrors, in Leo. This reduces the total mass to orbit and cuts system costs. Relays give other options, too.

Remember my column on Jim Baen and his electric spaceships? Well, the concept is being looked at; but the laser people think that instead of beaming power for orbit-to-orbit transfer with microwaves, which take very large antennae, why not use lasers? Thus the Earth to GEO, or Earth to Moon ship, could be powered by a
big
solar-cell array which doesn't go anywhere, with the energy sent by laser.

It's all very practical. It can work, and by that I don't mean that someday we'll be able to make it work—I mean it can work with what we have right now. Either the Sun-Hertzberg "dumb" system or the more sophisticated relay system could be started right now, carried to orbit by Shuttle payloads, and got into operation a few years after the Shuttle begins routine flights. It could be that close.

And if by now I haven't got you excited, I've failed; because just writing about this makes me want to run out and shout at people. It can happen. Right now, in our lifetimes. And think of the fallout benefits:

• • learning how to assemble large structures in space;
  
• • orbit-to-orbit transfer capabilities;
  
• • a space "construction shack."
  

There are a lot of others, of course. Scientific observations. As Phil Morrison told me last year, it's insane not to study the Sun; and the best way to do that is to get out there where you can see what's going on. But ignoring all those and just looking at the business opportunities, you can see mountains of payoffs.

Now what about the drawbacks? There are some, of course. First, you're dealing with gigawatts. The University of Washington laser-powered aircraft uses a 10 gigawatt laser power satellite. That's a lot of Watts to play with, and a big laser. What if it misses the airplane?

Well, it won't burn down Cleveland. It might start a fire, although the damage wouldn't be one ten-thousandth of the damage sustained by a crashing airplane. Matter of fact, because the aircraft are carrying so much less fuel on takeoff-and 92% of all aircraft accidents are within 5 minutes of takeoff or landing—if one
does
crash, the damage will be enormously less; and because of the reduced takeoff weight, the chances of accidents on takeoff are much reduced.

Then too, the frequency of the laser can be carefully selected so that the power will reach the airplane—it will not fly under laser power until it is at high cruising altitude—but can't reach the ground underneath. The atmosphere is pretty good at absorbing energy. Also, don't forget that the beam sweeps across the ground at something above the speed of the airplane, so that it's moving awfully fast.

But you do have a "sungun" in orbit, and in theory I suppose some madman could modify it to do considerable damage to the countryside below. Now by considerable damage I mean something comparable to an aircraft loaded with chemical bombs, understand; I don't even mean comparable to crashing a fully-loaded 747. And if the beam is constructed to radiate in frequencies that won't hit the ground, it is no simple matter to modify that laser to another frequency. Certainly that wouldn't be done secretly by one crackpot. It would take the entire satellite crew, and some of the ground personnel as well, all in a conspiracy.

And come to that—it doesn't take all that great a conspiracy to burn down a city with gasoline. Adding the satellite hasn't given potential terrorists any capability they don't have now, although it does give them a theoretically more spectacular one. On the other hand, one suspects it would be harder to enlist the satellite crew in such a conspiracy than it would be to subvert, say, the night watchman at a dynamite factory.

Effects of adding that energy to the upper atmosphere? Unpredictable. But we already add it, along with exhaust gasses, when we fly a conventional jet plane, so it's unlikely the laser will do more harm, and there's a lot of good reason to believe it will do none at all.

So much, then, for nuclear powered aircraft. They'll work, we can afford them—recall that
one
satellite controlling two and only two aircraft will pay for itself even at $1.00/gallon kerosene—and the concurrent benefits are incalculable but great. I love the idea. I hope somebody with the wherewithal to finance them will too.

Now what of "my" laser-powered spacecraft? (I hasten to add that I did not invent the concept; the work was done at Avco-Everett by A. N. Pirri and R- F. Weiss, working on a concept which seems first to have been studied by A R. Kantrowitz; I had their paper in front of me when I wrote HIGH JUSTICE.)

They'll work. At least that's the latest thinking. True, I seem to have made a mistake: the color of the laser is likely to be ruby red, from a CO
₂
laser, rather than blue-green as I have in my stories; and the launch site is likely to be a couple of thousand feet above sea level rather than down on the flat plains of Baja where I put it. Otherwise I seem to have got it pretty straight.

(There is not far from the Baja site I used for "my" launches a high plateau; purists may imagine that the launches happen there. Baja, with its tropic location and uninhabited areas to the east, remains a good site.)

I've described the concept before, and won't go much into detail here. Basically, one takes a capsule massing in the order of a metric ton and beams a lot of laser power up its tail. The report I heard at this conference was on an on-board reaction mass concept—the capsule carries fuel, which is heated by the laser energy. In my stories I used a "ramjet" effect for the initial phases of flight, with the laser heating air until the atmosphere was thin, after which it switches over to on-board reaction mass. I asked if the ramjet concept was rejected for cause or simply unstudied, and was told that there's no theoretical reason it won't work, it just hasn't been looked into, at least not by the speakers, D. H. Douglas-Hamilton and D. S. Reilly of AVCO Everett Research Laboratory.

So that's one that's still alive, and note the possibilities: if the laser-launching facility is constructed, the real costs to orbit have been absorbed. The flight article needn't be very expensive. Thus the prediction I sometimes make in my lectures, namely that within the lifetime of my student audiences a family can afford a space capsule which can be launched for them to live in, is still very much alive.

* * *

The conference produced a lot more. Some of the papers were on concepts that seem pretty far out even by
my
standard: how do you like windmills in space?

Imagine the following: a very large structure, looking like a "Dutch" windmill, but with blades hundreds of meters high. The solar wind—that stream of particles which constantly flows from the Sun, and which wasn't suspected until we had space probes—exerts enough pressure on the blades to turn the device. The "solar windmill" turns a generator, just as the Appropriate Technology Earthbound windmills do. Electricity is produced.

Sounds fantastic, doesn't it? And colorful, and quite pretty. Alas, it doesn't turn out to be very efficient. Note that I didn't say "impractical"; it would work, it just won't work as well as other devices would given the same investment. Still, I can see a time when solar windmills might be used as a quick-and-dirty power source kludged up by a space-faring family; perhaps a TV "Spacetrain" (something like a futuristic "Wagontrain") series will make use of the idea.

There were other papers describing far-out stuff which does look to be useful.

One of the problems with space power stations is heat.

Solar cells, and everything else for that matter, work on the principle of heat difference. The greater the difference in temperature between the front and the back sides of the solar cells, the more electricity they make.

Big lasers are not all that efficient, either, and must be cooled. On Earth that's a simple enough matter—run
"water
through the system, and either let the water flow on downstream, or pass it through a cooling tower for evaporation; either way the heat is dumped, carried away from the system of interest. (Yes, I know: that waste heat can be a problem for those who have to live with it. True, sometimes the "waste heat" turns out to be a blessing, as it has been for the marine life off New England during the winters of 76 and '77, but it wants watching; indeed, the prospect for getting unwanted waste heat off Earth entirely ought to make the conservation-minded become space enthusiasts.)

Out in space you certainly can't simply dump the heat by sending it "downstream" nor can you afford to use evaporative cooling. Evaporation would work, all right, and splendidly, but the major factor in any space system is the cost of transporting
anything to
orbit. You simply can't afford the transport costs of coolant.

Thus space structures must be cooled by radiation. In theory this is simple enough. After all, the night
sky
has an effective temperature wa-aa-y down there. In practice, though, it gets more difficult. It takes surface area to dump the waste heat, and surface area means mass and large structures; and those cost a bundle to put into orbit.

Comes now John Hedgepath, President of Astro Research Corporation of Santa Barbara. He's a no-nonsense structures man who takes the attitude of "you design the concept, I'll get it built."

The problem of waste heat has to do with density of structures; if you can have them heavy you have no problem, but since in orbit you can't, you want to get the mass per area down low.

__________

___________

Figure 28 shows some present-day figures. What's needed are structures with very large areas and very low weights; something in the order of 10 grams per square meter or better. That turns out to be possible, although it isn't easy.

Hedgepath presented another concept. Dust, it turns out, would be a marvelous radiating system. Dust has a
lot
of area for its weight.

Of course you can't throw dust away, just as you can't throw water away, not in space. The dust itself is valuable; any mass is. But suppose you take the dust and "throw" it across a couple of hundred meters or so; catch it, pass it through a heat exchanger to heat it up again, and throw the hot dust out to another catcher; and so forth. If you arrange the pitchers and catchers properly the net result is that the dust cools things down, but there is no motion imparted to the total system.

And that makes a dramatic picture: a tetrahedron in space, a kilometer or so high: bright lines on dark velvet. The lines are hot metallic powder (dust sounds better, doesn't it?) madly radiating the waste heat from another large structure a couple of kilometers long and half a kilometer wide. From the big solar-cell array bright beams stab down toward Earth to power an airplane skimming along at 50,000 feet and moving at 700 miles an hour.

It's colorful—and it's also practical.

Frank Coneybear, of Arthur D. Little, presented his own summary of trends in power transmission through lasers and such. He led off by saying "You can judge my faith in technology by the fact that I have my viewgraphs but I don't have my necktie: my necktie is wherever United Airlines has sent my luggage, but I carried my viewgraphs with me." He went on to summarize what's happening in laser technology and conclude that microwaves can certainly beam power down to Earth from satellite altitudes, and the technology is well-nigh off-the-shelf. However, lasers offer some big advantages, and the whole field of laser technology is exploding. There is the possibility of solar-pumped lasers, which will take sunlight (a
lot
of it, collected by a very large mirror) as their direct input.

The conference organizer, Ken Billman, is working on another direct use of sunlight: NASA's SOLARES project, which is a system of orbiting mirrors. The large mirrors concentrate sunlight onto a particular area on Earth, extending daylight by several hours a day; the effect is to increase the growing season. There is also the possibility of modifying climate through SOLARES.